The living room of the home accounts for a large portion of audiovisual experiences consumed by people, such as games, movies, music, and the like. While there has been a significant focus on visual displays for the home, such as high-resolution screens, large screens, projected surfaces, etc., there is significant unexplored territory in auditory display. Specifically, in all of the media mentioned above, a designer of the audio creates the content with a specific aural experience in mind. Acoustic conditions and speaker set up in a typical living room, however, are far from ideal. That is, the room modifies the intended acoustics of the audio content with its own acoustics, which can significantly reduce immersion of the soundscape, as unintended (and unforeseen) acoustics are mixed with the original intent of a designer of the audio. This unwanted modification depends on the placement of speakers, geometry of the room, room furnishings, wall materials, etc. For example, an auditory designer may wish for a listener to feel as if they are located in a large forest. Due to the point-source nature of conventional speakers, however, the listener typically perceives that forest noises are coming from a speaker. Thus, a large forest in a movie sounds as if it is located inside the living room, rather than the listener having the aural experience of being positioned in the middle of a large forest.
Generally, acoustics of a space can be mathematically captured by the so-called impulse response, which is a temporal signal received at a listener point when an impulse is played at a source point in space. A binaural impulse response is the set of impulse responses at the entrance of two ear canals, one for each ear of the listener. The impulse response comprises three distinct phases as time progresses: 1) an initially received direct sound; followed by 2) distinct early reflections; followed by 3) diffuse late reverberation. While the direct sound provides strong directivity cues to a listener, it is the interplay of early reflections and late reverberation that give humans a sense of aural space and size. The early reflections are typically characterized by a relatively small number of strong peaks superposed on a diffuse background comprising numerous low-energy peaks. A ratio of diffuse energy increases over the course of the early reflections until there is only diffuse energy, which marks the beginning of late reverberation. Late reverberation can be modeled as Gaussian noise with a temporally decaying energy envelope.
For convincing late reverberation, the Gaussian noise in the late reverberation is desirably uncorrelated between two ears of the listener. With conventional speaker setups, however, even if late reverberation emanating from speakers is mutually uncorrelated, the binaural response for any given speaker is correlated between the two ears, as both ears received the same sound from the speaker (apart from acoustic filtering by the head and shoulders). As this occurs for all speakers in the room, a net effect is a muddled auditory image somewhere between the original intended auditory image versus a small space restricted inside the speakers or within a room.
A technique referred to as crosstalk cancellation has been utilized to address some of the shortcomings associated with conventional audio systems. Generally, crosstalk cancellation has been used to allow binaural recordings (those made with microphones in the ears and intended for headphones) to play back over speakers. Crosstalk cancellation methods receive a portion of a signal to be played over a left speaker and feed such portion to the right speaker with a particular delay (and phase), such that it combines with the actual right speaker signal and thus cancels the portion of the audio signal that goes to the left ear. Conventional systems, however, restrict the position of the listener to a relatively small space. If the listener changes position, artifacts are generated, negatively impacting the experience of the listener with respect to presented audio.